The rate of cooling per H_{2} molecule (erg s^{-1}) is defined as

where *E _{vJ}* >

The Fortran program interp.f
prerforms an interpolation to any given set of values of the following parameters, within
their specified ranges:

n_{H} |
(1) | ||

T | (2) | ||

n(H)/n(H_{2}) |
(3) | ||

n(ortho)/n(para) |
(4) |

These parameters are, successively: *n*_{H} = *n*(H) + 2*n*(H_{2}),
the gas density; the kinetic temperature, *T*; the H to H_{2} density ratio;
the ortho- to para-H_{2} density ratio. The program interp.f prompts for values of
these four parameters. The cooling function is calculated by interpolation of the data
contained in the file le_cube
and is returned as . The ranges specified above are
exceeded at the risk of the user: no guarantee of the reliability of the result is given,
even if the output value appears "reasonable". The subroutines used to evaluate
the cooling function may be incorporated (along with the data set le_cube) in the user's
own astrophysical model.